In the processing of fluids, such as water and waste water, it is necessary to remove (or separate) materials from the fluids to render the fluids suitable for use or reuse. The materials may initially be in, or mixed with, the fluids, such as liquid or water or water-like fluids typically found in clarifiers, flocculators or other liquid treatment plants. For example, clarifiers that are referred to as settlers, promote settling of the material to the bottom of a basin. The material is first collected from the fluids by flat plates or hollow tubes of the settlers. Generally, the material to be removed includes particles that are denser than the fluid, or that are processed to become denser than the fluid. As a result of the density difference, the particles move downwardly under the force of gravity as the fluid and the particles flow. This type of material is referred to herein as “settleable-particles”. The fluid with this type of material (settleable-particles) is referred to herein as “particle-laden fluid”, or “settleable-particle-laden fluid”. Also, references herein to “fluid” are references to such “particle-laden fluid” and “settleable-particle-laden fluid”, except for “cleaner fluid”, which is the “particle-laden fluid” and “settleable-particle-laden fluid” from which some of the settleable-particles have been removed (as by settling), and except for “clean fluid”, which is the “particle-laden fluid” and “settleable-particle-laden fluid” from which most (if not all) of the settleable-particles have been removed (as by settling).
A simple settleable-particle removal process slowly flows the particle-laden fluid through a long basin (e.g., a 100 foot long basin). The force of gravity (FG) acts downwardly on the settleable-particles, which move toward and to the bottom of the basin through a settling distance that is generally equal to the depth of the fluid in the basin (e.g., 10 feet). The settleable-particles that are moving toward the bottom may be referred to as “settling-settleable-particles” (or “settling-particles”) until they reach (i.e., settle to) the bottom of the basin. The particles at (and on or near) the bottom of the basin may be referred to as “sludge” or “settled-particles”. Sludge is characterized by a greater density of the settleable-particles in a given volume than when the settleable-particles are flowing in the fluid or settling from the same given volume of the fluid. To successfully remove settleable-particles from high numbers of gallons per minute (GPM) of such flowing fluid by such settling through the exemplary ten foot settling distance, the area of the floor of such basins for fluid flow and settling must be unacceptably great (e.g., 3 square feet for 1 GPM).
In attempts to substantially reduce such area required to settle the settleable-particles from such fluids, various clarifier apparatus have been proposed for use in the basins. One type of proposed clarifier apparatus is a settler having at least two closely-spaced (e.g., 1 inch) flat thin-edge plates. The flat thin-edge plates have thin edges to allow a flow of particle-laden fluid into a narrow (e.g., 1 inch high) flow channel between the two closely-spaced flat thin-edge plates. As proposed, the flat thin-edge plates were horizontal, but as described below this proposed horizontal approach has to Applicant's knowledge never been successfully implemented even though the narrow flow channel enables a settling depth to be very short (e.g., slightly less than the narrow 1 inch height of the flow channel). As proposed, settleable-particles would settle through such settling depth onto a lower plate of the two flat thin-edge plates. Upon settling onto the lower flat thin-edge plate, the settleable-particles would form the sludge. Because the proposed flat thin-edge plate would be horizontal, there was a theoretical but unrealized benefit of somewhat shortening the length of the fluid-flow distance (e.g., horizontal) required to separate the settleable-particles from the particle-laden fluid to form the sludge on the lower flat thin-edge plate.
However, problems have arisen in attempts to make practical use of the theoretical design of these proposed closely-spaced horizontal flat thin-edge plates. For example, the flow channel between two of these proposed flat thin-edge plates is very narrow (i.e., the 1 inch). It was intended that the settleable-particles would settle onto the flat thin-edge lower plate, and would form the more dense sludge on the flat thin-edge horizontal lower plate. As a result, the intent of the proposed two closely-spaced flat horizontal thin-edge plates was to confine the ongoing flow of the fluid through the narrow flow channel in the same space (or volume) that is occupied by the sludge. This proposed ongoing fluid flow would thus have a flow rate that would increase as the thickness of the settled sludge increases. The increase in the flow rate would be in a direction of the flow (e.g., an X direction), which is undesirable because it requires more flow length (in the X direction) to settle the settleable-particles from a fluid flowing at a high flow rate as compared to fluid flowing at a lower flow rate. This requirement is due to the higher flow rate fluid carrying the sludge in the narrow flow channel above the lower flat thin-edge plate, where such carrying would be in the X direction of the fluid flow. The higher flow rate would not allow the settling to occur rapidly in the downward (or Z) direction of the force of gravity (FG). This carrying of the sludge in the X direction would offset (reduce) the benefit of attempting to shorten the settling length (in the X direction), and would make it necessary to increase the length and thus the area of these types of proposed settlers. In other words, the ongoing higher flow rate of the fluid through the same narrow flow channel space as is occupied by the sludge would tend to carry the sludge through that same space in the X direction of the fluid flow and would require more flow length in the X direction to do the same amount of settling.
There are also disadvantages of attempts to overcome these problems of the closely-spaced flat thin-edge plates of the above-described proposed horizontal settlers. For example, a standard, widely-used closely-spaced flat-and-inclined-thin-edge-plate settler orients two closely-spaced flat thin-edge plates on an incline of about fifty-five degrees with respect to the horizontal to define a steep upward flow of fluid and settleable-particles. As a result, particles that have settled onto the lower flat-and-inclined-thin-edge plate tend to be moved down the incline by a (non-vertical) component of the force of gravity FG. This component acts parallel to the steep incline, so that the settled-particles are caused to move down the steep incline and fall out from between the closely-spaced flat-and-inclined-thin-edge plates onto a bottom of the basin below the closely-spaced flat-and-inclined-thin-edge-plates. On the bottom, the settled-particles form the sludge.
Despite wide use of the closely-spaced flat-and-inclined-thin-edge-plates, and despite improvements, disadvantages remain, such that there is still a need to improve the closely-spaced flat-and-inclined-thin-edge-plate settlers. For example, an effective settling area of a settler is a horizontal area. The effective settling area of the lower inclined-and-flat-thin-edge-plate onto which the particles settle is based on less than 100% of the inclined length of that lower inclined-and thin-edge-plate because a value of this effective settling area is a function of the cosine of the incline angle (e.g., less than one). At a 55 degree incline angle, the effective settling area is about 0.5 times the inclined length. As a result, not all of the inclined length of the inclined-and-flat-thin-edge-plates contributes to the effective settling area for collection of the settled-particles (sludge). Also, as the settling-particles are moved by the component of the force of gravity FG down the incline and fall out from between the two closely-spaced inclined-and-flat-thin-edge-plates onto the bottom of the basin, the falling settling-particles cross (i.e., intersect) a typical inlet flow stream of incoming settleable-particles and fluid. Such inlet flow stream is referred to herein as “dirty-flow” and may include, for example, non-settleable particles. Such dirty-flow flows along and somewhat above the bottom of the basin. Part of this dirty-flow enters an open bottom end of a flow channel between two closely-spaced inclined-and-flat-thin-edge plates. This dirty-flow may tend to carry settling and already-settled particles upwardly between the closely-spaced inclined-and-flat-thin-edge plates, which reduces the efficiency of the settling operation.
What is needed then is a way to more efficiently separate settleable-particles from particle-laden fluid. The needed way would avoid cross flow of settling-particles and settled particles with incoming dirty-flow entering the settler. Also, the needed way would promote rapid settling of the settled-particles from the flow stream to shorten the required settling length of the settler. The needed way would also reduce a tendency of the flow of cleaner-fluid within the flow channels to carry settled-particles horizontally or upwardly along the flow channels. Further, the needed way would provide practical methods and apparatus for removing the settled-particles (sludge) from between closely-spaced plates of a settler.